Many people usually believe that they do not need a co-founder, and some believe that giving away half of the equity is also losing a big chunk of the startup. That seems to be a short sighted view. Even VC's prefer startups who have at least 2 or more founders when they are investing. YC also encourages in selecting startups which have 2 or more founders, though they do sometimes find solo founder startups too (still they recommend during the batch to find one).

Now many of you usually say that you don't need a founder during the initial stage, just build the mvp and then get a co-founder once you have traction and there is pmf. This might be a smart move, but then again during this period attracting co-founders is a lot easier. The hard part is already done, the first steps of struggles have already been taken. You will get a lot of people interested to join you now. But somewhere in the back of the head, you have a little doubt that would this co-founder have stood by me if we were starting from scratch? Are they here to ride along the wave now since initial traction has already started?

There is no particular problem in bring in co-founders at any stage of the startup. Some big ones brought co-founders even 3-4 years down the line, because they felt they were essential for their startup.

But the founders who stick from the start, have a more special bond and have each others back during the struggles and no traction period too. Not that these types of startups do not fall, or the bond between the founders will stay intact forever. It's just that you know you have something special and magical, because they believed in the idea when nobody else ever did. It is less transactional, and more about standing up for each other during the lowest of times. This is why, the most ideal co-founders are mostly found around your circle whom you've known for at least a few months or years personally.

PS: There are no hard rules that one will always work and other won't. Finding a co-founder is like matching with a date. It can convert into a long term relationship or even get ghosted or even cheated on. It is always a mix of right timing, the right place and a bit of luck.